Geologic History of the Delamarva Peninsula

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U Odyssey This


Belemnites are fossil cephalopods related to the squids, octopods and cuttlefish that live in the ocean today. Belemnites went extinct at the same time as the dinosaurs — about 65 million years ago, but their fossil remains are easy to find at the C&D Canal. Because they are so plentiful in Delaware, the belemnite Belemnitella americana was named the State Fossil of Delaware in 1996.


Living cephalopods are soft bodied animals that are related to snails, clams, and chitons. Unlike their relatives, cephalopods have a greatly reduced shell that is contained inside their body. In squids this reduced, internalized shell is called a gladius; in cuttlefish it is the cuttlebone.

The brown, cigar-shaped belemnite you find in a fossil pit is not the whole animal. When you hold a belemnite, you are holding part of the ancient internalized shell!


This internalized shell had three parts. The brown, cigar-shaped part is called the rostrum, or guard. This part would have been found at the very back of the animal, between the fins. The chambered phragmocone was found inside the rostrum, which is why some belemnites look hollow. A sword-shaped proostracum was attached to the rostrum, towards the head of the animal. Because the phragmocone and proostracum had a different chemical composition than the rostrum, they are not well-preserved in the fossil pits.

Cephalopods are exclusively marine animals, so finding fossil cephalopods on land is evidence that the Delamarva Peninsula was once an underwater marine environment!

great white shark

We don’t normally think of sharks as prehistoric animals. Yet these perfect machines of the sea have been swimming in the oceans for hundreds of millions of years. Sharks, or their ancient ancestors, first appeared about 445 million years ago in the Late Ordovician Period. As a group they have adapted to their surroundings in very remarkable ways. The shark’s sleek muscular body and several rows of sharp teeth allowed them to easily hunt and capture other prehistoric marine animals for food. About 360 million years ago during the Carboniferous Period sharks had risen to dominate the oceans.

Shark tooth Close-up

Prehistoric sharks and their modern relatives have a soft internal skeleton made up of cartilage. Unlike bone, cartilage does not easily become a fossil. Without a fossilized bone structure, scientists have relied on other hard parts of ancient sharks to identify them. The good news for scientists was that sharks’ teeth and scales were hard and could easily fossilize. Both ancient and modern sharks have plenty of teeth that they lose on a regular basis. The teeth fell to the bottom of the sea floor, became trapped in the sediments, and fossilized.

Fossilized sharks teeth have been found all over the world. At first, people did not know that they came from sharks. They thought they were the tongues of ancient birds. In the 1770s scientists began to systematically study fossils. These scientists, known as paleontologists, grouped the fossils into categories. They identified these prehistoric fossils as shark’s teeth. Because they could date the rock formations that the teeth were found in the scientists were able to determine when the sharks lived.

great white shark tooth

Several times in their long history large numbers of sharks have gone extinct, including at the end of the Permian Period (245 million years ago), at the end of the Triassic Period (208 million years ago), and at the end of the Cretaceous Period (64 million years ago). At each of these extinction events some shark species survived and were able to adapt to new conditions. For example, one ancient shark known as Carcharodon megalodon grew to over 40 feet long and weighed up to 20 tons. It lived from 24 to 1.6 million years ago. While many ancient sharks were quite large, the sharks living today are smaller. The largest, such as the Great White Shark, might grow to 20 feet in length. The modern shark is highly specialized and has a complex biology.

Sharks’ teeth helped unravel the geologic history of the Delmarva Peninsula. By finding fossilized sharks’ teeth in the sedimentary rock layers beneath the surface soils of the Peninsula, scientists determined that the Peninsula was once covered by the ancient Atlantic Ocean.

Shark Teeth at the C & D Canal
By: Jason Barrowclough

One kind of fossil that can be found at the C & D Canal are shark teeth. These shark teeth are about 65-85 million years old and are from the late Cretaceous period — that is as old as the dinosaurs! There are many different varieties of teeth from extinct sharks that can be found here. Some of the species are:

shark tooth dig

Once at the C & D Canal, you will want to stop by the spoil piles. Spoil piles are mounds of dirt that get dumped off after the canal gets dredged, and that’s where you find the fossils. For most people, it takes a while to train their eyes when looking for fossils. The shark teeth will be small, usually dark colored, and shaped like a triangle. Even though people have been collecting at the C & D Canal for many years, there are still many, many shark teeth to be found, so just stay determined and you’re sure to spot them.

The reason there are so many teeth around is because sharks shed their teeth all the time. Unlike humans, who only have two sets of teeth, sharks go through hundreds of teeth throughout their lifetime. Sharks are constantly growing new teeth, because when shark teeth get too old, they just fall out, and a new tooth replaces the old one. So if you count the hundreds of shark teeth coming out of a single shark, and count all of the sharks in the area, over a couple million years, that’s a lot of shark teeth.

Questions and Answers:

Q: How can you tell the difference between fossil shark teeth and more recent teeth?

A: First, I would like to point out that the chance of finding a recent shark tooth is much lower than finding a fossil in this location, so if you have found a shark tooth, chances are it is a fossil shark tooth. On top of that, the fossil shark teeth are usually black to brown in color, but can also be tan, and on occasion, other various colors. Recent shark teeth are plain white.